13.4.2 LINGUAS in po/

The po/ directory should also receive a file named
LINGUAS. This file contains the list of available translations.
It is a whitespace separated list. Hash-marked comments and white lines
are ignored. Here is an example file:

# Set of available languages.
de fr

This example means that German and French PO files are available, so
that these languages are currently supported by your package. If you
want to further restrict, at installation time, the set of installed
languages, this should not be done by modifying the LINGUAS file,
but rather by using the LINGUAS environment variable
(see Installers).

It is recommended that you add the "languages" ‘en@quot’ and
‘en@boldquot’ to the LINGUAS file. en@quot is a
variant of English message catalogs (en) which uses real quotation
marks instead of the ugly looking asymmetric ASCII substitutes ‘`’
and ‘'’. en@boldquot is a variant of en@quot that
additionally outputs quoted pieces of text in a bold font, when used in
a terminal emulator which supports the VT100 escape sequences (such as
xterm or the Linux console, but not Emacs in M-x shell mode).

These extra message catalogs ‘en@quot’ and ‘en@boldquot’
are constructed automatically, not by translators; to support them, you
need the files Rules-quot, quot.sed, boldquot.sed,
en@quot.header, en@boldquot.header, insert-header.sin
in the po/ directory. You can copy them from GNU gettext’s po/
directory; they are also installed by running gettextize.